How do you determine higher priority in the Cahn-Ingold-Prelog convvention?

The higher the atomic number, the higher priority

What is the (E) configuration?

the highest priority groups are on the opposite side of the double bond

What does the 'E' stand for in the Cahn-Ingold-Prelog Convention?

entgegen

What is the (Z) configuration?

The highest priority groups are on the same side of the double bond

What does the 'Z' stand for in the Cahn-Ingold-Prelog Convention?

zusammen

Which configuration of alkenes is more stable?

Trans

What increases the stability of alkenes?

The greater the number of attached alkyl groups, the greater the alkenes stability

Cycloalkenes containing 5 carbon atoms or fewer exist only in _____ form

cis-

Why have Trans-cyclohexene and trans-cycloheptene not been iscolated?

Because they have a very short lifetime

What mechanism does dehydrohalogenation promote?

E2 mechanism

How to favor an E2 mechanism?

Use a secondary or tertiary alkyl halide if possible (because steric hinderance in the substrate will inhibit substitution)

When a snthesis must begin with a primary alkyl halide, use a bulky base (because the steric bulk of the base will inhibit substitution)

Use a high concentration of a strong and nonpolarizable base, such as an alkoixide (because a weak and polarizable base would not drive the reaction toward a bimolecular reaction, thereby allowing unimolecular processes (such as SN1 or E1 reactions) to compete

Sodium ethoxide in ethabol and potassium tert-butoxide in tertbutyl alcohol are bases typically used to promote E2 reactions

Most elimination reactions follow Zaitsev's rule in which the ost stable alkenes are the major products. However, under some circumstances, the major elimination product is the less substituted, less stable alkene

Stereochemistry of E2 reactions

The 5 atoms involved in the transition state of an E2 reaction (including the base) must lie in the same plane

The anti coplanar conformation is the preferred transition state geometry

The anti coplanar transition state is staggered (and therefore of lower energy), while the syn coplanar transition state is eclipsed

Orientation requirement- H and Br have to be anti periplanar (trans-coplanar)

E2 elimination where there are two axial beta hydrogens

Both Ha and Hb hydrogens are anti t the chlorine in this, the more stable conformation

What is dehydration?

Loss of a molecule of water

What happens when an alcohol is dehydrated?

It forms an alkene when heated with a strong acid

What do the temperature and concentration of acid required to dehydrate an alcohol depend on?

Depends on the structure of the alcohol substrate

What is the most difficult alcohol to dehydrate?

Primary alcohols

What is the easiest alcohol to dehydrate?

Tertiary alcohol

What happens to some primary and secondary alcohols during dehydration?

Can undergo rearrangements of their carbon skeletons during dehydration